Multiple spindle automatic bar machines generally employ collet chucks for holding end working tools such as drills, spot drills, center drills, counterbores, spot facers, combination drills and countersinks, reamers, end mills and hollow mills, the integral shanks of the chucks being longitudinally adjustably clamped in the end working tool slides (or auxiliary slides thereon) which are moved toward and away from the spindle carrier. The use of end working tool chucks of the character indicated adds substantially to set-up time in that it entails individual measurement and longitudinal adjustment of the tools in the respective chucks or of the tool holders in the end working tool slides to achieve predetermined dimensions of the ends of the tools with respect to the spindle drum face of the machine in the closed position of the end cutting tool slide or slides.